Actively Controlled Exercise Device

ABSTRACT

An actively controlled exercise device provides a dynamic force responsive workout. The device includes: a user output arm movably attached to a base frame; an actuator attached between the user output arm and the base frame, the actuator including a motor and an output shaft connected to the user output arm; at least one position sensor attached to the actively controlled exercise device adjacent to the user output arm for detecting a position and velocity of the output arm; a load cell attached to the actively controlled exercise device adjacent to the actuator for detecting a force exerted on the user output arm; and a force controller in communication with the position sensor, the load cell, and the actuator for activating the actuator to impart a force on the user output arm during an exercise repetition.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims priority to U.S. Provisional Patent ApplicationSer. No. 62/237,162 for “A System for Actively Controlled ExerciseEquipment” to Lee Magnusson et al. and filed on Oct. 5, 2015, thecontents of which are incorporated herein by reference in its entirety.

FIELD

This disclosure relates to the field of fitness devices. Moreparticularly, this disclosure relates to a fitness device and system forproviding a dynamically adjusted force for optimizing a workout and forcollecting, storing, and transmitting data related to activity of thedevice.

BACKGROUND

Strength training and exercise are old and established institutions.However, significant new wisdom on tools, techniques, and trainingcontinue to evolve on a continuing basis. More knowledge of how muscle,connective tissue and joints operate is available now than ever.Numerous theories are available on how strength is improved and how toprevent injury. There is a significant opportunity to combine thisknowledge with improved exercise technology to achieve goals faster,safer, and more efficiently.

The problem of building strength requires a versatile approach. Buildingstrength is a non-linear process that is dependent on the person, theirmuscle, their history, and their current state. Fixed weight or fixedforce exercises often provide short term increases but most people willquickly plateau, or level off with their training.

Traditional strength training machines do not provide an effective,safe, and efficient workout for a number of reasons. First, because offriction in the system, the eccentric phase of the workout is at a forcelower than the concentric phase. Second, the chance of injury on aweight machine can be high due to the large, instantaneous forces thatmay be exerted onto human joints. These forces can lead to short termmuscle and tendon injury, and long term joint problems. Finally, using agravity influenced mass to create force adds considerable bulk andweight to the design of a machine.

What is needed, therefore, is a fitness device and system for providinga dynamically adjusted force for optimizing a workout and forcollecting, storing, and transmitting data related to activity of thedevice.

SUMMARY

The above and other needs are met by a force controlled exercise device.In a first aspect, an actively controlled exercise device is providedhaving: a user output arm movably attached to a base frame and movablein at least a first exercise direction and a second exercise direction,wherein the first exercise direction corresponds to concentric work of amuscle of the user and the second exercise direction corresponds toeccentric work of the muscle of the user; an actuator attached betweenthe user output arm and the base frame, the actuator including a motorand an output shaft connected to the user output arm; at least oneposition sensor attached to the actively controlled exercise deviceadjacent to the user output arm for detecting a position and velocity ofthe output arm; a load cell attached to the actively controlled exercisedevice adjacent to the actuator for detecting a force exerted on theuser output arm; and a force controller in communication with theposition sensor, the load cell, and the actuator for receiving data fromthe at least one sensor attached on the actively controlled exercisedevice and, in response to position, velocity, and force data receivedfrom the position sensor and load cell, activating the actuator toimpart a force on the user output arm during an exercise repetition.

In one embodiment, the actuator is a linear actuator. In anotherembodiment, the actuator is a ball screw linear actuator.

In yet another embodiment, the exercise device further includes both atleast one encoder sensor and one force sensor, wherein the forcecontroller activates the actuator based on data detected by both theforce sensor and encoder sensor.

In one embodiment, the position sensor is an absolute position encoder.

In another embodiment, the force controller instructs the actuator toimpart a force in the second eccentric work direction that is greaterthan the force imparted on the first concentric work direction.

In yet another embodiment, the force controller activates the actuatorto impart a ramped force on the user output arm such that the force isat a minimum when velocity is detected as zero and gradually increaseswhen velocity is detected as being greater or less than zero.

In one embodiment, the force controller activates the actuator to imparta positive force when the position sensor detects the user output arm tobe at a first position, and wherein the force controller activates theactuator to impart a negative force when the position sensor detects theuser output arm to be at a second position.

In another embodiment, the force controller activates the actuator tomove the user control arm along a fixed position and time path, andwherein data related to a force of the user on the user control arm isdetected by the load cell adjacent to the actuator.

In one embodiment, the force controller imparts a short perturbanceforce on the actuator during an exercise and detects a position andvelocity response of the user through the user output arm.

In a second aspect, an actively controlled exercise device is providedhaving: a user output arm movably attached to a base frame and movablein at least a first exercise direction and a second exercise direction,wherein the first exercise direction corresponds to concentric work of amuscle of the user and the second exercise direction corresponds toeccentric work of the muscle of the user; an actuator attached betweenthe user output arm and the base frame, the actuator including a motorand an output shaft connected to the user output arm; at least oneposition sensor attached to the actively controlled exercise deviceadjacent to the user output arm for detecting a position and velocity ofthe output arm; a load cell attached to the actively controlled exercisedevice adjacent to the actuator for detecting a force exerted on theuser output arm; and a force controller comprising a processor andcomputer readable storage and in electronic communication with theactuator, position sensor, and load cell, the force controller includingone or more instructions executable on the processor for detectingposition, velocity, and force data from the position sensor and loadcell, in response to detected position, velocity, and force data,activating the actuator to impart a force on the user control arm, andadjusting a force imparted on the user control arm based on one of adetected position, force, and velocity of the user control arm.

In a third aspect, a method of actively controlling an exercise deviceis provided, the method including the steps of: providing a user outputarm movable in relation to a base frame; providing at least one encodersensor and force sensor in communication with the user output arm fordetecting a position and velocity of the user output arm and a forceimparted on the user output arm; providing an actuator in mechanicalcommunication with the user output arm; providing a force controller inelectrical communication with the encoder sensor, force sensor, andactuator; detecting a position and velocity of the user output arm withthe encoder sensor; detecting a force exerted on the user output arm bya user with the force sensor; activating the actuator to impart a forceon the user control arm based on a detected position, velocity, andforce of the user control arm, wherein the force is greater when theuser control arm is determined to be moving in an eccentric workdirection and less when the user control arm is determined to be movingin a concentric work direction.

BRIEF DESCRIPTION OF THE DRAWINGS

Further features, aspects, and advantages of the present disclosure willbecome better understood by reference to the following detaileddescription, appended claims, and accompanying figures, wherein elementsare not to scale so as to more clearly show the details, wherein likereference numbers indicate like elements throughout the several views,and wherein:

FIGS. 1 and 2 show a controlled exercise machine according to oneembodiment of the present disclosure;

FIG. 3 shows a cross-sectional side view of a ball screw actuatoraccording to one embodiment of the present disclosure;

FIG. 4 shows a diagram of operation of a controlled exercise machineaccording to one embodiment of the present disclosure;

FIG. 5 shows a diagram of workout force applied on a traditional workoutmachine according to one embodiment of the present disclosure;

FIG. 6 shows a force velocity diagram of an eccentric workout routineaccording to one embodiment of the present disclosure;

FIGS. 7 and 8 show diagrams of eccentric workout routines having rampedforces according to one embodiment of the present disclosure;

FIG. 9 shows a diagram of a position-time profile of a workout routineaccording to one embodiment of the present disclosure;

FIG. 10 shows a force and position profile of a workout routine usinganti hysteresis control according to one embodiment of the presentdisclosure;

FIG. 11 shows a force and position profile of a workout routine usinganti hysteresis control according to one embodiment of the presentdisclosure;

FIGS. 12 and 13 show diagrams of the Hill Model of muscle according toone embodiment of the present disclosure;

FIG. 14 shows a diagram of the Hill Model of muscle plotted as a surfacewith respect to position and velocity;

FIG. 15 shows an example of muscle model control for keeping a userwithin a specific range of position and velocity according to oneembodiment of the present disclosure;

FIG. 16 shows a target region of muscle control according to oneembodiment of the present disclosure;

FIG. 17 shows a schematic of weight bounce during an exercise accordingto one embodiment of the present disclosure;

FIG. 18 shows a position versus time plot of an exercise by a userduring a bounce movement according to one embodiment of the presentdisclosure;

FIG. 19 shows a diagram of a force due to weight bounce and positiontrajectory according to one embodiment of the present disclosure;

FIG. 20 shows a flat loading force according to one embodiment of thepresent disclosure;

FIG. 21 shows an example of a variable inertia control according to oneembodiment of the present disclosure;

FIG. 22 shows a diagram of a resulting reduced impact force of anexercise with inertia scaling according to one embodiment of the presentdisclosure; and

FIGS. 23-26 show diagrams of applying perturbations in force during anexercise according to one embodiment of the present disclosure.

DETAILED DESCRIPTION

Various terms used herein are intended to have particular meanings. Someof these terms are defined below for the purpose of clarity. Thedefinitions given below are meant to cover all forms of the words beingdefined (e.g., singular, plural, present tense, past tense). If thedefinition of any term below diverges from the commonly understoodand/or dictionary definition of such term, the definitions belowcontrol.

A system for actively controlling a machine assisted workout is providedthat addresses many deficiencies in traditional strength trainingmachines. The system for actively controlling a machine assisted workoutimproves both strength training and recovery from an injury by providingactively controlled adaptable and customizable loads, highly variableloads that encourage strength through muscle confusion, improved safety,and motivation of a user.

FIG. 1 shows a basic embodiment of an actively controlled exercisemachine 10 for strength training or rehabilitation. The activelycontrolled exercise machine 10 includes a user output arm 12, a baseframe 14, an actuator 16, a force sensor 18, and an encoder 20. Theactively controlled exercise machine 10 provides a dynamicallycontrolled force matching a twitch force of a user's muscle. By matchingforce in the manner described herein, an exertion experienced by a usermay be linearized thereby resulting in more even distribution of forceover the total length of contraction (concentric stage) and relaxation(eccentric stage) of the muscle. A force controller in communicationwith the actuator, force sensor, and encoder provides controlledreal-time feedback to a user for a force controlled workout. Theactively controlled exercise machine 10 adaptively responds to muscleexertion of the user to decrease muscle and joint strain of the usertypically caused by high, short term loads. By adaptively responding toforce generated by user that would cause a high load on muscle andjoints, the high instantaneous load can be spread over a longer periodof time, and reducing the peak load. Reducing the peak load reduces thestretch rate of the viscoelastic muscle.

Referring to FIGS. 1 and 2, the user output arm 12 is shaped to engagean appendage of a user during an exercise. The user output arm 12includes a pair of grips 22A and 22B extending from arm bars 24A and24B. Padding such as a rubber or foam layer formed over the grips 22Aand 22B may be included to enhance a grip of a user on the grips 22A and22B. Grips 22A and 22B may be adjustable attached to the arm bars 24Aand 24B to allow a user to adjust a position of the grips 22A and 22Brelative to the user. For example, the grips 22A and 22B may bethreadably engaged with one or more bores 25 formed through the arm bars24A and 24B. The arm bars 24A and 24B are attached with a cross-member26 extending between the arm bars 24A and 24B such that the user outputarm 12 is substantially U-shaped.

The above described orientation of the user output arm 12 is configuredfor a bench-press type workout of a user, wherein the user engages thegrips 22A and 22B to push the user output arm away from the user duringconcentric work of the user's chest and supporting muscles and to resistreturn of the user output arm 12 towards the user during eccentric workof the user's chest and supporting muscles. While the above descriptionis suitable for bench-press exercises, it is also understood that theuser output arm 12 may be formed into a configuration suitable for othertypes of workouts. For example, the user output arm 12 may include oneor more pads or other like portions for contacting legs or otherappendages of the user during leg exercises. Such configurations areknown and may be readily adapted to the actively controlled exercisemachine 10 of the present disclosure.

The base frame 14 includes one or more structural members 28 forsupporting a seat 30 and backrest 32. One or more leveling feet 34 arealso attached to the structural members 28 for stabilizing thecontrolled exercise machine 10 on a floor surface. An enclosure 36 maybe formed along one of the structural members 28 for supporting andcontaining a force controller of the controlled exercise machine 10discussed in greater detail below. The structural members 28 may beformed of a metal, such as steel or aluminum, and may have a rounded orrectangular cross-sectional area.

With further reference to FIGS. 1 and 2, the user output arm 12 ismovably attached to the one or more structural members 28 such that theuser output arm 12 is supported by the structural members 28 and movablein relation to the structural members 28 during a user exercise. Theuser output arm 12 may be pivotally attached to one of the structuralmembers 28 such that when a user engages the grips 22A and 22B of theuser output arm 12, the user output arm 12 moves in relation to thestructural members 28.

The encoder 20 is attached to the controlled exercise machine 10 betweenthe structural members 28 and the user output arm 12 such that theencoder 20 detects a position of the user output arm 12 relative to thestationary base frame 14. The encoder is preferably an absolute positionencoder, however it is also understood that various other positionsensors may be used to capture data relative to a position of the useroutput arm 12. The encoder provides absolute position data of the outputarm 12 and further provides a velocity of the output arm 12 based onchanges in position of the output arm over a given time.

The actuator 16 is attached to the controlled exercise machine 10between the user output arm 12 and the stationary base frame 14.Referring to FIG. 3, the actuator 16 is preferably a ball screw linearactuator having a mounting bracket 38, a housing 40, a motor core 41 andmotor 42 supported on a rotor bearing 43 within the housing 40, and aball screw shaft 44 located at least partially within and extending fromthe housing 40. A ball nut 46 engages the ball screw shaft 44 and issupported by a thrust bearing 48. A housing cap 50 is placed on an endof the housing 40 and includes an aperture 52 to allow the ball screwshaft 44 to extend through the housing cap 50. The motor 42 engages theball nut 46 to rotate the ball nut 46 and thereby cause the ball screwshaft 44 to either extend or retract from the housing 40. A positionencoder 53 detects a position of the actuator 16.

The actuator is attached at the mounting bracket 38 to the structuralmembers 28 and at an end of the ball screw shaft 44 to the user outputarm. The force sensor 18 preferably comprises a load cell locatedbetween the housing and the mounting bracket 38 for detecting a forcebetween the actuator 16 and the user output arm 12. While the figuresillustrate the force sensor 18 being located adjacent to the housing 40of the actuator 16, it is also understood that the force sensor 18 maybe located in various other positions such that the force sensor 18 maydetect a force between the user output arm 12 and the actuator 16. Forexample, the force sensor 18 may be located within hand grips 22A and22B, or adjacent to a point at which the user output arm 12 is attachedto the base frame 14.

Referring again to FIG. 1, the controlled exercise machine 10 includes aforce controller 58 that is in electronic communication with theactuator 16, the force sensor 18, and the encoder 20 for controlling anactivation of the actuator based on data received from the force sensor18 and encoder 20. The force controller 58 includes a processor and acomputer readable storage mediums. Further, executable instructions maybe stored on the computer readable storage medium and executed by theprocessor to activate the actuator in response to a force or position ofthe user output arm 12 as discussed in greater detail below. The forcecontroller 58 may activate and adjust a force of the actuator based ondetected user input and a force of the user's muscles on the user outputarm 12 to provide a dynamic exercise that is in response to forceimparted on the controlled exercise machine 10 by the user.

Actively Controlled Strength Training

The problem of building strength requires a versatile approach. Buildingstrength is a non-linear process that is dependent on the person, theirmuscle, their history, and their current state. Fixed weight or fixedforce exercises often provide short term increases but most people willquickly plateau, or level off with their training. An activelycontrolled machine using force and position feedback provides for muchgreater versatility and matching to an individual's needs. Effectivestrategies of strength training are available using the controlledexercise device 10 disclosed herein. As shown in FIG. 4, the controlledexercise device 10 is controlled based on an interaction of a mechanicallinkage of the device that is controlled by the actuator 16. Theactuator 16 is controlled by the force controller, which receivesfeedback from sensors throughout the system to guide characteristics ofthe device. System data may be transmitted to a centralized data store.

Intra-Rep Control

Within a single repetition, various effective workouts are available forstrength training using the controlled exercise device 10. It is widelyreported that muscle is strengthened mostly during eccentric work andnot during concentric work or isometric exercise. Eccentric work is theportion of a lifting cycle in which the weight is lowered as the muscleis lengthened. Concentric work is the opposite, the shortening of themuscle and positive work portion of a lifting cycle. Isometric exerciserefers to holding a fixed force or weight at constant position. Physicaltrainers will often recommend eccentric work as a means of strengtheningfor recovering from an injury. For example, a recommended AchillesTendinitis recovery exercise is to do calf raises, using both calves tolift the body but a single calf to lower. This gives double the amountof eccentric work applied to the muscle as concentric work. Mostly allstandard free-weight based exercises are designed to provide equalconcentric and eccentric work. Weight machines in fact produce lesseccentric work than concentric work due to friction of theirtransmissions. This is illustrated by the force-velocity profile in FIG.5. The actively controlled weight machine however is designed to beinfinitely variable and it can provide a force-velocity profile typicalof strength building calf workout described above.

One control strategy is to switch between levels of force depending onvelocity, wherein a negative velocity represents eccentric work and apositive velocity represents concentric work.

$F = \left\{ \begin{matrix}F_{e} & {{{if}\mspace{14mu} v} \geq 0} \\F_{e} & {{{if}\mspace{14mu} v} < 0}\end{matrix} \right.$

This is shown graphically in FIG. 6. It is easy to extend this style ofcontrol to include a ramped change in force near zero velocity as shownin FIGS. 7 and 8. This helps make for a less abrupt transition for theuser and also helps to improve stability and reduce chatter around zero.It is also relevant to note here that this force vs velocity profilecould take any shape as may be desired for the workout. A few moreexamples are decreasing force with speed to help prevent the user fromgoing too fast. A target velocity range in which force may be providedthat is either higher or lower than normal to target specific muscles.Alternatively, a user could program to match a certain muscle model asdescribed further herein.

Using active control, forces may be designated in specific regions ofposition, velocity, or acceleration. So a training strategy could be toset force levels to target specific regions. In one mode of control, aposition vs force ramp is used when changing force levels to helpmaintain stability and provide a smoother user experience. Whendirection changes in the positive direction force ramps to lower leveland when direction changes is the negative direction force ramps to ahigher level, using position as the control variable for the ramp. Theramp could take any shape, such as sigmoidal. An example anti-hysteresiscontrol is shown below using Python code:

def force_hysteresis (pos,step,fc,fe) : ftmp =-step*(pos-force_hysteresis.pos_last) + \ force_hysteresis.f_last fdes =min(max(ftmp,fc),fe) force_hysteresis.f_last = fdesforce_hysteresis.pos_last = pos return(fdes) force_hysteresis.pos_last =0 force_hysteresis.f_last = 0 step = 1./.4 # force per position F_hyst =zeros (shape(t)) for i,p in enumerate(pos): F_hyst[i] =force_hysteresis(p,step,fc,fe)Resulting plots for a specific example using this control are shown inFIGS. 9-11.

Other methods of applying eccentric force may be further defined, suchas time based control wherein the force controller switches force levelsat designated times to encourage a particular cadence and positionthreshold wherein the force controller will activate the actuator tomaintain the user output arm in a certain spatial position in responseto user force. Changes in force may be according to a time-based forceramp or other methods of smoothly changing a force of the actuator.

In one mode, the force controller may activate the actuator to maintaina fixed position versus time profile. This profile could be any shape.The user would try to apply maximum effort in both eccentric andconcentric directions. Resulting force vs time, averages and otherparameters would be displayed to the user and logged for furtherinformation. This would provide useful information for fitnessevaluation of a user. Further, applying various positions and speedcould be used to identify parameters for a target muscle of a user. Theparameters may be presented in various forms, such as by providingmaximum power or force expected for a designated number of repetitions.Differences between users muscles and standard models may be identifiedsuch that routines performed on the controlled exercise machine 10 maytarget deficient areas.

In another mode of operation, the controlled exercise machine mayprovide muscle model control workouts. It is known that muscle has aforce-position-velocity relationship. This relationship depends on manyfactors including the type of muscle, its condition, genetics, and islikely specific on a per person basis. In general terms the Hill MuscleModel does a good job explaining the phenomenon seen with muscle, thoughmany other models are available and could be used in our controlstrategy. An ideal exercise for a muscle would be to apply forcesproportional to the muscle's ability at any given time, position, andvelocity. It so happens that the muscle model predicts that forceability is much greater in the negative velocity region, so this form ofcontrol would likely include eccentric style workouts as describedabove.

The Hill Muscle Model looks at both active and passive force as afunction of position and velocity. Active force is produced by thecontractile elements and passive force is due to muscle stretch. TheHill Muscle Model predicts that force has an inverse parabolicrelationship as a function of position. The model also predicts lowpassive force until a threshold distance and then an increase in passiveforce with position. These two relationships are plotted in FIG. 12. Inaddition, the Hill Model predicts force as a function of velocity aswell. This equation is given as follows:

(v+b)(F+a)=b(F ₀ +a)

where a and b are parameters that fit to a specific muscle. Thisequation is plotted in FIG. 13.

Next both the position dependence and the velocity dependence of forcecan be plotted on a single 2 d plot as shown in FIG. 14. Amultiplicative contribution of the two contributions was assumed here,but more general models need not make that assumption. Now our musclemodel control can measure both position and velocity and apply a forceproportional to the values of the model at those position and velocityvalues. This will provide for a very effective loading of the muscle aswell as a natural eccentric workout. Other interesting workouts includeusing the muscle model but targeting specific regions as shown withexamples in FIGS. 15 and 16. As illustrated in FIG. 12, the region isdefined as 0.5<v<0.3 and 0.3<p<0.1. In the positive velocity region highforce is applied outside the target region, which pushes the user backinto the target region. In the negative velocity region, 0 force isapplied outside the target region, which signals the user that they havegone outside the target region (note that applying high force here aswith positive velocity would end up pulling the user farther from thetarget). The boundaries in these examples are sharp and dramatic butcould also be smooth and less pronounced. Information about the user'sposition in the model space and in the regions could also be providedthrough the graphical user interface, sound, and/or haptic feedback.

In addition to the model itself which relates force to muscle length,appropriate corrections may also be applied to map from muscle length tolimb position, and for the applicable moment arms of the muscle withrespect to the joint center of rotation. Values could be presented tothe user and analyzed/controlled in any space (muscle length space,joint angle space, or task space).

The muscle model can also be used in other ways. By applying atrajectory in position control mode as described above, the user's forcecan be measured. This trajectory could traverse the space of positionand velocity such that an accurate muscle model could be created for thespecific user. This model could either be a direct map with interpolatedvalues between directly measured values, or it could be used to fitparameters for standard models to the user. The muscle model could alsobe created simply by applying any type of control and tracking themeasured responses from the user. The model could be kept up to datewith every workout as well and used as a means for tracking progressover time.

There are several other suitable muscle models in existence. Any of themis relevant for applying control as described above. One other class ofkey importance is muscle fatigue models. These relate force output vstime and previous history. Models of this sort will be beneficial toadjust the force applied as a function of reps. A decrease in force withreps is sometimes referred to as “tapering.” A model could help predictoptimal tapering, but may also be used to change and track the routinein other ways as well. In addition, a model of this sort could be usedto track the user during their workout and/or between workouts todynamically update the workout.

In order to provide a realistic feel for the user it may be beneficialfor the actively controlled force to simulate a virtual inertia. Thiswould be given by setting a control force as follows:

F _(a) =m _(v) *{umlaut over (x)}

The virtual inertia could be positive, zero, or negative, or a functionof other variables such as position, velocity, and time. Negativeinertia control provides an interesting exercise which targets stabilityproducing muscles.

The controlled exercise machine 10 of the present disclosure may furtherassist in impact reduction control. It is well known that people tend tobounce weights and/or use momentum during exercise. Examples includeswinging a weight up during a curl exercise or allowing a weight toincrease in velocity during the eccentric phase of a bench press, thenallowing the weight to bounce off the passive elasticity in the musclewhich helps with the concentric phase. These techniques cause a varietyof problems. They can reduce the effectiveness of the workout byreducing the load placed on the muscle in key areas, they can cause therecruiting of muscles other than the target muscles, they can increasethe impact loading applied to tendons and joints as described below,they can be more dangerous due to the dynamic balance required, and theycan simply look uncool at the gym. With an actively controlled forcemachine these impact forces can be reduced or removed through a varietyof different control techniques. An example is provided here. A typicalweight bounce is shown schematically in FIG. 17. Any example of theposition vs time seen during a bounce is shown in FIG. 18. Thistrajectory created by the inertia and the user inputs then creates aforce, which is shown in FIG. 19. Note that the high peaks are due tothe impact on the muscle. The lower peaks occur when the mass is up.There is a decrease in force as the weight is accelerated in thedownward direction. So not only does this movement cause high impactforces which can cause injury, it also reduces the load on the userduring raising and lowering the weight, which reduces the exerciseseffectiveness. One method for preventing the inertial bounce completelyis to have the force controller actively control a force only withoutsimulate inertia. By controlling force directly, the result would be aperfect constant force as shown in FIG. 20. The user may prefer not tohave zero inertia for reasons of stability and feel. In this case onetechnique we could use is to set a variable inertia, for example onewhich scales with velocity as shown in FIG. 21. This inertia scalingcreates the reduced impact force seen in FIG. 22.

Other means to reduce the impact force include controlling momentumrather force, using damping to absorb elastic energy, using negativestiffness to cancel bounce, and/or any other actively controlled means.We could set effective high inertia on change in direction to bleed offbounce energy. We could control momentum by zeroing out effectivemomentum on changes in direction. We could set controlled stiffness,damping and inertia as a function of position velocity and/or force toaddress the issue.

In addition, a model of muscle such as the 3 element Hill Model may beuseful. The model could be inverted such that the effect forces wouldhave on passive tissues/springs could be calculated. Then forces wouldbe applied by the actuator to attempt to prevent energy storage in thepassive tissues.

In another embodiment, transient force control may be used to applytransient forces greater than normal throughput the routine, possiblyrandomly. A force blip of this sort may help to tear and thus buildmuscle while the user is already at their maximum sustainable force.

Further, an application programming interface may be provided such thatpersonal trainers and users can program in their own routine. Thisroutine could use any number of previously mentioned controllers.

Inter-Rep Control Strategies

This section refers to strategies that are used to string togethermultiple reps into a set. Other control features will include theability to change control force between repetitions or sets. Forexample, force might taper with progressing repetitions or sets toattempt to keep the user at maximum ability.

Pre-programmed warm-up routines will help prepare the user for higherloads. These routines are also useful for quick workouts, demos, andfitness tests.

In a tempo training program, the controlled exercise machine 10 willencourage the user to maintain a specific movement tempo. Visual, audio,or haptic feedback will help the user adhere to a given tempo byproviding cues. A display timer will also demand a certain amount ofrest between sets.

Muscle Confusion

Muscle confusion training is also provided by the controlled exercisemachine 10. Exercise parameters would change on a per repetition, perset, per workout, or cross-workout basis so that the user would not knowwhat exercise to expect. The machine might present 3 reps with highforce towards the top of the travel range and 3 reps with high forcetowards the bottom of the travel range. Again a programming interface isprovided for users and trainers to set up their own inter-rep routinesfor infinite variations.

Other Concepts

Other features of the controlled exercise machine 10 include dataanalytics collection. For example, user action may be converted intometrics describing their force, position, speed and related values.During the use of the system, analytic data generated by the system isstored. This stored data captures the characteristics of the workout.This data can then be analyzed en masse to determine commonalities fromwhich one can derive the principle components of effective techniques.Further muscle performance may be tracked such as speed vs. force vs.position.

The controlled exercise machine may detect weak spots and use those weakspots to predict injuries before they occur. Workout routines canspecifically target weak spots. Multi-axis force sensors may be used tomonitor force on each limb and force direction to identify favoringand/or joint alignment problems.

The controlled exercise machine 10 may further be in electroniccommunication with a database for collecting multi-user data. Thecontrolled exercise machine may bin users into categories in how theyreact to strength training. Data may be used to find out what types ofworkouts are working best for different bins.

Single user data may also be collected to display previous workoutinformation on a display of the machine and used to encourage a user tobest previous workout values.

An application program interface (“API”) may be provided to createworkouts. Trainers may sell workouts in an application store environmentand the workouts may be compatible with the controlled exercise machine10. Users or trainers may share workouts with friends, or initiatechallenges which may be in the form of games.

Data from the controlled exercise machine may also be utilized for gymscheduling. Multiple users may schedule use of the device, and sets maybe scheduled to alternate with other users. Users selects to start aworkout and then is scheduled to go through a series of exercises whichwill not interfere with other users. May have to wait for a time slot tobe available.

Safety

Various safety features may be included on the force controller forcontrolling the controlled exercise machine such as voice shutoff,automatic shutoff, automatic decrease in force, variable inertia, muscletuning as described above, vision, and personal customization.

Motivation

A key requirement for achieving fitness is to maintain motivation. Thismachine will include a user interface which helps motivate users tobring to the gym and complete their exercises.

Muscle Model and State Testing

In one embodiment, the controlled exercise machine of the presentdisclosure may be used to determine an individual's muscle model andmuscle state. During an exercise, the actuator may apply a small, nearlyinstantaneous perturbation in force experienced by the user. Theperturbation in force applied on the controlled exercise machine on theuser may take the form of a step increase or decrease in force byapproximately 10%, and may remain at that level for a period of between10 ms and 1 second before returning to an initial value as shown in FIG.23.

A response of the user to the force perturbance is determined bydetecting a change in position of the user output arm 12 in response tothe perturbance. As shown in FIG. 24, near instantaneous changes inposition (less than 50 ms) due to change in force that align with theperturbance are detected. By measuring the instantaneous change inposition due to the force perturbance, a muscle's stiffness may besampled and otherwise analyzed, which is a function of both a strengthof the muscle and its activation level. By analyzing instantaneouschanges in velocity and position, muscle damping parameters may beidentified. When observing position and velocity changes on a scalegreater than 50 ms (FIGS. 25 and 26), a neurological muscle controlmodel may be obtained which provides insight into the individual'smental state during an exercise. Both physical and muscle properties anda neural model may be used to tailor an exercise routine both on aninter-rep/inter-set control basis and on a long term training strategybasis using the control method described herein.

Example Machine

An actively controlled, actuated exercise machine for strength and/orrehabilitation is provided. The machine uses an actuator that isconnected mechanically to an output arm. The user applies force to theoutput arm to conduct exercises. The machine incorporates sensors whichsense the state of the sys-tem, useful for actively controlling theactuator as described above and collecting information as describedabove. Nominally those sensors are either position/velocity sensors thatmeasure either the position/velocity of the actuator orposition/velocity of the output arm or they are force sensors whichmeasure force applied by the user or force output by the actuator. Thesystem includes an actuator controller that reads values of the sensorsand applies active control to the actuator based on the readings.

An example machine, which has chest press exercise functionality isshown in FIGS. 1 and 2. However, the machine could be any number ofother arrangements to exercise other muscles or other standardexercises. The machine could also be multiple degree of freedom in orderto provide more variable trajectories and/or free/floating degrees offreedom. The additional degrees of freedom could be underactuated, fullyactuated, or overactuated. Examples of other exercises to perform couldbe leg press, shoulder press, ab crunch, leg extension, leg curl, bicepscurl, triceps extension, back extension, leg ab/adduction, and calfraise as examples.

The example machine of FIGS. 1 and 2 uses a motor coupled to a ballscrewfor actuator. The ballscrew is connected to a pin joint would moves theoutput arm. The output arm is constrained to rotate around a pin jointwith respect to the ground/base frame and thus has a single actuateddegree of freedom. The user sits in the seat and pushes on the outputarm producing a chest press exercise. An absolute encoder positioned atthe arm/ground joint measures arm position for use with controlalgorithms and data collection. A force sensor is located so as tomeasure the force output of the actuator/the force output of the personfor control algorithms and data collection.

Other various features may include a log-in system that allows the userto both recall and save data specific to the individual's use of themachine. The login mechanism can include wireless, contactlesscommunication via an RF signal. The RF scheme may be, but is not limitedto Near Field Communication (NFC), 802.11 wi-fi, RFID, or similartechnology. Other methods include magnetic stripe, magnetic key, or aPIN code input. The login mechanism could be provided by a user's phoneor by a supplied tag that could be inserted into a wrist mounted holder.

The controlled exercise machine 10 may include powered adjustablemachine settings—seat height, arm width, leg length, etc. that moveautomatically when user logs into machine. By associating the userlog-in data with known traits of the user, the machine is able toautomatically initialize and configure itself in a manner conducive tothe individualized use of the specific person who is logged in. Thesesettings can include but are not limited to the height, weight, force,and mode of operation. These overall settings can be further adjusted onan individual machine, such that exact preferences can be stored on aper-machine basis. For example, the initial length of an arm grasp canbe set for that user. Further, the machine can adjust the display to aposition that provides an ergonomic comfort to the user.

To improve the system of the device, the user will have severalmechanisms to immediately control the dynamics of the machine. One wayis to have an emergency stop button. This “E-stop” button, accessible atall times, has the effect of shutting down the applied force of thesystem. Another approach is to have a soft stop available by voicecommand. This would allow the user to shut down the applied force byspeaking a specified command, which would be received by a microphone onthe machine and translated into a command to stop the force. To preventerrant behavior from other nearby users, the microphone system couldconsist of an array of microphones to localize the voice command to theintended range of an active user of the machine.

In operation, a user is seated on the controlled exercise machine 10 andengages the grips 22A and 22B of the output arm 12. As the user places aforce on the user output arm 12, that force is detected by the forcesensor and received on the force controller. The force controllerdetects the force, and further detects a position and velocity of theoutput arm using the encoder. Depending on a desired workout to beperformed, in response to the detected force, position, and velocity,the force controller activates the actuator to impart a force on theoutput arm to create desired resistance for the user. The forcecontroller continues to run a feedback loop in which parameters arecontinuously evaluated and a force provided by the actuator adjusted tomaintain the force experienced by the user within a desired range.

The controlled exercise device of the present disclosure advantageouslyprovides a dynamic adjustment of force on a user during a workout tooptimize strength training of the user. Depending on the desiredworkout, the actuator is activated by the force controller in responseto detected force, velocity and position data. Because the force may bevaried by the actuator without the necessity of additional weights, anoverall weight of the machine may be reduced compared to traditionalweight exercise machines.

The foregoing description of preferred embodiments of the presentdisclosure has been presented for purposes of illustration anddescription. The described preferred embodiments are not intended to beexhaustive or to limit the scope of the disclosure to the preciseform(s) disclosed. Obvious modifications or variations are possible inlight of the above teachings. The embodiments are chosen and describedin an effort to provide the best illustrations of the principles of thedisclosure and its practical application, and to thereby enable one ofordinary skill in the art to utilize the concepts revealed in thedisclosure in various embodiments and with various modifications as aresuited to the particular use contemplated. All such modifications andvariations are within the scope of the disclosure as determined by theappended claims when interpreted in accordance with the breadth to whichthey are fairly, legally, and equitably entitled.

What is claimed is:
 1. An actively controlled exercise devicecomprising: a user output arm movably attached to a base frame andmovable in at least a first exercise direction and a second exercisedirection, wherein the first exercise direction corresponds toconcentric work of a muscle of the user and the second exercisedirection corresponds to eccentric work of the muscle of the user; anactuator attached between the user output arm and the base frame, theactuator including a motor and an output shaft connected to the useroutput arm; at least one position sensor attached to the activelycontrolled exercise device adjacent to the user output arm for detectinga position and velocity of the output arm; a load cell attached to theactively controlled exercise device adjacent to the actuator fordetecting a force exerted on the user output arm; and a force controllerin communication with the position sensor, the load cell, and theactuator for receiving data from the at least one sensor attached on theactively controlled exercise device and, in response to position,velocity, and force data received from the position sensor and loadcell, activating the actuator to impart a force on the user output armduring an exercise repetition.
 2. The actively controlled exercisedevice of claim 1, wherein the actuator comprises a linear actuator. 3.The actively controlled exercise device of claim 2, wherein the actuatorcomprises a ball screw linear actuator.
 4. The actively controlledexercise device of claim 1, comprising both at least one encoder sensorand one force sensor, wherein the force controller activates theactuator based on data detected by both the force sensor and encodersensor.
 5. The actively controlled exercise device of claim 1 whereinthe position sensor comprises an absolute position encoder.
 6. Theactively controlled exercise device of claim 1, wherein the forcecontroller instructs the actuator to impart a force in the secondeccentric work direction that is greater than the force imparted on thefirst concentric work direction.
 7. The actively controlled exercisedevice of claim 1, wherein the force controller activates the actuatorto impart a ramped force on the user output arm such that the force isat a minimum when velocity is detected as zero and gradually increaseswhen velocity is detected as being greater or less than zero.
 8. Theactively controlled exercise device of claim 1, wherein the forcecontroller activates the actuator to impart a positive force when theposition sensor detects the user output arm to be at a first position,and wherein the force controller activates the actuator to impart anegative force when the position sensor detects the user output arm tobe at a second position.
 9. The actively controlled exercise device ofclaim 1, wherein the force controller activates the actuator to move theuser control arm along a fixed position and time path, and wherein datarelated to a force of the user on the user control arm is detected bythe load cell adjacent to the actuator.
 10. The actively controlledexercise device of claim 1, wherein the force controller imparts a shortperturbance force on the actuator during an exercise and detects aposition and velocity response of the user through the user output arm.11. An actively controlled exercise device comprising: a user output armmovably attached to a base frame and movable in at least a firstexercise direction and a second exercise direction, wherein the firstexercise direction corresponds to concentric work of a muscle of theuser and the second exercise direction corresponds to eccentric work ofthe muscle of the user; an actuator attached between the user output armand the base frame, the actuator including a motor and an output shaftconnected to the user output arm; at least one position sensor attachedto the actively controlled exercise device adjacent to the user outputarm for detecting a position and velocity of the output arm; a load cellattached to the actively controlled exercise device adjacent to theactuator for detecting a force exerted on the user output arm; and aforce controller comprising a processor and computer readable storageand in electronic communication with the actuator, position sensor, andload cell, the force controller including one or more instructionsexecutable on the processor for: detecting position, velocity, and forcedata from the position sensor and load cell; in response to detectedposition, velocity, and force data, activating the actuator to impart aforce on the user control arm; and adjusting a force imparted on theuser control arm based on one of a detected position, force, andvelocity of the user control arm.
 12. A method of actively controllingan exercise device, the method comprising: providing a user output armmovable in relation to a base frame; providing at least one encodersensor and force sensor in communication with the user output arm fordetecting a position and velocity of the user output arm and a forceimparted on the user output arm; providing an actuator in mechanicalcommunication with the user output arm; providing a force controller inelectrical communication with the encoder sensor, force sensor, andactuator; detecting a position and velocity of the user output arm withthe encoder sensor; detecting a force exerted on the user output arm bya user with the force sensor; activating the actuator to impart a forceon the user control arm based on a detected position, velocity, andforce of the user control arm, wherein the force is greater when theuser control arm is determined to be moving in an eccentric workdirection and less when the user control arm is determined to be movingin a concentric work direction.